This invention relates to the production of antibodies. More particularly, it relates to a method of inducing an immune response in an experimental animal by introducing into the animal cells which produce and secrete an antigen.
Antibodies are now widely used in the purification of biological materials and in diagnostic testing and have recently been used therapeutically to treat certain types of lymphomas and melanomas. The production of antibodies against a specific antigen has been approached in the prior art by injection of the antigen into an experimental animal, typically two or more times, and then harvesting antibody from serum. More recently, with the advent of hybridoma technology, rather than collecting antibody from the animal's circulatory system, a sample of lymphocytes is taken from the animal, typically from the spleen, and the cell sample is fused with an immortal cell line such as a myeloma. The fusion products are screened to detect viable hybridomas which secrete the antibody. These hybridomas are then cultured to produce colonies from which relatively large quantities of monoclonal antibody may be harvested.
One important factor in the foregoing procedure is the degree of purity of the antigen used to induce the immune response. Where one seeks antibody complementary to a specific biological material produced by cells, concentration and purification of the particular antigen from the wide variety of proteins, glycolipids, glycoproteins, lipoproteins, and polysaccharides that are typically present in the secretions is often both tedious and a key factor in successful production of the antibody of interest. To the extent the sample of antigen used for immunization contains extraneous materials, the immunized animal produces a large number of antibodies of differing specificity, only a small portion of which constitute the antibody of interest. Consequently, purification of the antibody from the antisera is tedious. Furthermore, if one seeks a lymphocyte which is producing the antibody of interest, it is necessary to employ elaborate screening procedures to detect the subset of cells of interest. Additionally, purification of the antibody of interest from bleedings or isolation of a subset of lymphocytes producing the antibody of interest is simplified if the immunizing agent comprises a relatively pure antigen sample.
In the production of antibody to a non-secreted material, e.g., a cell surface antigen (immunoglobulin), or antibody intended for purification of substances produced by cells, e.g., interferons, it is now within the skill of the art to produce a genetically modified cell line which secretes the surface antigen or larger amounts of the interferon. Purification of the cell secretions to concentrate the material of interest and to remove at least some extraneous material is nevertheless desirable or mandatory.
Recently, as reported, for example, by Hatzubai et al. (Journal of Immunology, Vol. 126, No. 6, June, 1981), and Miller et al. (New England Journal of Medicine, Mar. 4, 1982, page 517), a promising method for treating certain types of lymphoma has been developed. The technique is based on the observation that tumors result from the uncontrolled proliferation of clones of (B) cells that express on their surfaces markers restricted to an immunglobulin molecule, including, in part, a structure characteristic of the lymphoma clone. The distinguishing immunoglobulin region (idiotype) of each lymphoma clone is substantially unique and can distinguish tumor cells from normal cells in the patient. The tumor cells do not secrete the idiotype-bearing immunoglobulin molecule, but its secretion can be induced by fusing the lymphoma cell with a myeloma cell line. The resulting fusion products (hybridomas) are screened for secretion of the idiotype-bearing immunoglobulin. A simplified screening procedure is disclosed in co-pending application Ser. No. 613,235, the disclosure of which is incorporated herein by reference.
After culturing and harvesting of a crude product, the idiotype is purified by various chromatography techniques and experimental animals are injected with a small dose of the monoclonal idiotype product followed by a booster injection at 3-4 weeks later. A few days thereafter, the animal's spleen is removed and spleen cells are fused with, e.g., a myeloma cell line. After screening and cloning, anti-idiotype antibody is collected and purified in quantities sufficient for therapeutic use. Intravascular injection of about 150 mg of antibody has been associated with extended remission.
The requirement for antibody tailored to each patient puts serious constraints on this cancer treatment approach. As noted in Miller et al.'s paper (referenced above), more streamlined procedures for producting these anti-idiotype antibodies would be likely to facilitate using anti-idiotype antibodies in this clinical treatment.